Humans often act irrationally as a consequence of biasing influences

Irrational behaviour arises as a consequence
of emotional reactions evoked when faced with difficult decisions,
according to
new research at UCL (University College London), funded by the Wellcome
Trust. The UCL study suggests that rational behaviour may stem from
an ability to override automatic emotional responses, rather than an
absence of emotion per se.

It has long been assumed in classical theories of economics that people
act entirely rationally when taking decisions. However, it has increasingly
become recognized that humans often act irrationally, as a consequence
of biasing influences. For example, people are strongly and consistently
affected by the way in which a question is presented. An operation
that has 40% probability of success seems more appealing than
one that has a 60% chance of failure.

In the study, published in the journal Science, UCL researchers used
a gambling experiment to establish the cognitive basis for rational
decision-making. The goal of the task was to accumulate as much money
as possible, with the incentive of being paid in real money in proportion
to the money won during the experiment. Participants were given a starting
amount of money (£50) at the beginning of each trial. They were
then asked to choose between either a sure option or a gamble option
(where they would have a certain chance of winning the entire amount,
but also of losing it all). Subjects were presented with these choices
under two different frames (i.e. scenarios), in which the sure option
was worded either as the amount to be kept from the starting amount
("keep £20"), or the amount to be deducted ("lose £30").
The two options, although worded differently, would result in exactly
the same outcome, i.e. that the participant would be left with £20.

The UCL study found that participants were more likely to gamble at
the threat of losing £30 than the offer of keeping £20.
On average, when presented with the "keep" option, participants
chose to gamble 43% of the time compared with 62% for
the "lose" option. Furthermore, there was a marked difference
in behaviour between participants. Some people adopted a more rational
approach and gambled more equally and consistently under both frames,
while others showed a real aversion to risk in the "keep" frame
while at the same time displaying high risk-seeking behaviour in the "lose" frame.

Brain imaging revealed that the amygdala, a region thought to control
our emotions and mediate the 'fight or flight' reaction,
underpinned this bias in the decision process. Moreover, the UCL study
revealed that people with more rational behaviour had greater brain
activity in the prefrontal cortex, a region known to be involved in
higher-order executive processes, suggesting that their brains are
better able to incorporate their emotions into a more balanced reasoning
process.

Mr Benedetto de Martino, of the UCL Institute of Neurology, said:

" It
is well known that human choices are affected by the way in which a
question is phrased. For example, saying an operation carries an 80%
survival rate may trigger a different response compared to saying that
an operation has a 20% chance of dying from it,
even though they offer exactly the same degree of risk.

_ Our study provides neurobiological
evidence that an amygdala-based emotional system underpins this biasing
of human decisions. Moreover,
we found that people are rational, or irrational, to widely differing
amounts. Interestingly, the amygdala was active across all participants,
regardless of whether they behaved rationally or irrationally, suggesting
that everyone experiences an emotional reaction when faced with such
choices. However, we found that more rational individuals had greater
activation in their orbitofrontal cortex (a region of prefrontal cortex)
suggesting that rational individuals are able to better manage or perhaps
override their emotional responses."

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